Field of the Invention
The present invention relates to a three-dimensional shape measuring apparatus and a control method thereof which acquires three-dimensional shape data of an object to be measured by projecting pattern light onto the object to be measured, and capturing an image of the object.
Description of the Related Art
A three-dimensional measuring apparatus, which acquires three-dimensional shape data of an object to be measured by providing a projector apparatus and capture apparatus in a given relationship, projecting a plurality of pattern light beams from the projector apparatus onto the object to be measured, and capturing an image of the object to be measured by the capture apparatus every time the pattern light is projected, is known.
For example, Japanese Patent Laid-Open No. 2007-192608 (to be referred to as a literature hereinafter) discloses a technique for acquiring three-dimensional shape information of an object to be measured by projecting a plurality of binary patterns onto the object to be measured so as to code a three-dimensional space.
When light enters a photodetection element such as a CCD image sensor used in an image capturing device, a signal according to a light intensity is obtained, and unavoidable shot noise is typically generated at the same time. This shot noise influences the precision of position detection of a pattern. Especially, when an intensity of light which enters the image capturing device is weak, since the shot noise is large relative to the light intensity, an S/N ratio drops, thus lowering the position detection precision of a pattern to be detected.
By increasing an exposure amount on the image capturing device when an image is captured, the influence of this shot noise is lightened, and the position detection precision can be improved. However, in a three-dimensional shape measurement which projects a plurality of patterns, when an increase in exposure amount on the image capturing device is adjusted based on a light source luminance level on the projection side, electric power increases unwantedly. When the increase in exposure amount is adjusted based on an exposure time when an image is captured, it takes time until shape measurement, thus posing a problem.